What is this treatment called (pic inside)

[LUNAJEWELS]

I'm sorry If I posted in the wrong forum but I was wondering if anyone knew what this treatment was called? Is it black gold or silver and is it used today? Also, if it's not.. does anyone know what era it would belong in...Georgian .. etc?

Thanks in advance

 

[pyramid]

The metal on the band looks quite soft and marked. It looks like tarnished silver to me. Just guessing.

There is black rhodium plating that is sometimes a finish on modern rings but it looks very dark black and not
like that at all.

Platinum can look gun metal color when it has a patina but this looks different to that to me.

 

[ruby59]

I may be way off, but are you talking about oxidizing a piece of jewelry to give it an antique look?

 

[LUNAJEWELS]

Yep I thought it was black silver?

I like the antique look it has